Recovery of oil from oil-bearing geologic formations in many instances requires the use of large quantities of water. Water is injected into such formations to facilitate moving the oil from the formation and delivering it to the surface where the oil and water are separated. In some applications, the water is used one time, cleaned appropriately for stream discharge, and discharged. Waste cleaned from the water is commonly placed in a landfill. The cost and environmental concerns have provided impetus for both reusing the water and reducing the volume or waste material to be landfilled.
In the well-known “Steam-Assisted Gravity Drainage” approach to heavy oil recovery, two horizontal wells are drilled into a formation. One of the wells, known as the injection well, is disposed above and spaced apart from the other well, known as the collection well. Water in the form of steam is directed into the injection well where the steam condenses and gives off sensible heat that warms the oil in the formation. The warming of the oil reduces the oil viscosity and adhesion to rock in the formation. A mixture of oil and water flows into the collection well from whence it is removed to the surface. The oil and water are separated, and the separated water, commonly referred to as produced water, is prepared for reuse. Reuse, of course, entails making steam, in many cases high quality steam. So, preparing the produced water for reuse requires removing contaminants from the produced water. Such contaminants include those that can lead to scaling and fouling steam generation equipment. Present means of preparing the produced water for reuse produces significant quantities of wet waste, and landfilling such wastes is both expensive and environmentally challenging. Improved means are needed to reduce the volume of wastes in such applications.